Don't aim left!!!!!
Most of us want to aim left to adjust for the slice and that can be ok in certain circumstances but when you are either playing or practicing the best thing to do to help your slice is, don't aim left. A slice happens when a sidespin is put on the ball, causing it to curve to the right for a right-handed player and to the left for a left-handed player. Sidespin to the right is caused when the clubface is open (pointed right) relative to the path the club is traveling as the club impacts the ball. This not only causes sidespin but also a glancing blow, which causes issues with direction and distance.
Fixing the slice should be simple, right? Just get the clubface square at impact, and we’re good. Not so fast! Often, years of slicing comes with years of that particular golfer teaching themselves to compensate so they can tolerate the slice. An example of compensation would be a golfer aiming their shoulders to the left, which, in turn, caused their swing path to go to the left. Thus, simply fixing the clubface might cause a golfer to hit pulls directly to the left. There are two common flaws that cause most slices: grip and alignment.
You are more likely to slice with your driver because drivers create less backspin and has the potential to generate more sidespin (depending on how open or closed the clubface is at impact). Lofted clubs create more backspin, which partially negates sidespin. Drivers have the least loft, so they mitigate sidespin much less. The longer your club, the more chances you have of slicing the ball.
Fixing your slice
The first thing you can do to fix your slice is adjusting your grip. Most golfers when they first learn golf, are taught a neutral grip, the grip where your thumbs point straight down the club and are in line with each other.
Most high handicappers and slicers have a weak or neutral grip. Their hands are more on top of the club when they take their grip. Start by putting your left hand on the grip in your normal position, then rotate it to your right until you see two to three knuckles when looking down at address. Next, take your right hand and place it more under the club's grip - making it "stronger."
This makes it easier for you to close the clubface, and you should see your shots going dead straight if done right.
Re-aligning yourself and your ball position can straighten your shot
Very often, a slicer will point their shoulders, feet, and hips to the left of their target. When a person’s hands are rotated away from the target on the grip, many times this gets their shoulders a little closer to aligned properly but usually not exactly where we want them. Getting the feet, hips, and shoulders all parallel with the target line will make it much easier for the student to swing the club down the line, as opposed to across the line.
Position the ball off the inside of your front foot, about even with your heel, to promote an upward strike of the golf ball. Striking the ball on the upswing will help promote a straighter flight and greater distance. Most slices with the driver result from a downward angle of attack, which produces weak distance and a slicing spin. Set up to the ball with your head a few inches behind the ball to help promote an upward strike.
With your head behind the ball and your right hand grip below the left, you'll have a natural tilt in your shoulders at address. The proper shoulder tilt at address will promote a good shoulder turn on the backswing. Keep the club face square as you swing through impact. Don't allow the club to rotate over as you swing through impact. Keep turning your hips until you finish your swing. Your belt buckle should face the target at your finish position.